Telephone system



Sept. 1, 1925.

v I... 0.. KELLOGG TELEPHONE SYSTEM Filed Jan. 14. 1921 VJ A 6 a lq 127765772011" fimg/ZZ fi i/fly Patented Sept. 1,1925.

' UNITED ems-E4 LEROf n. KELLOGG, or DE RF'IEL ILLINOIS, KSS$GNOR 'ro KELIlOGG swrronBonnn AND SUPPLY COMPANY, or cII o Gw LL NoIsn conroRArr oN or ILLINOIS.

wriitnrfionn sys'rnni.

Application filed niiiiaiyi ,smai' m5. 437,211.

To all whom it'mag 00mm;-

Be it known that I, LER Y KELLOGQ, a citizen of the United States ofyAmerica and resident of Deerfield, county of Lake, and State of Illinois, have invented pemmrnew and/ useful Improvementsin] Telephone Systems, of which the following' isa speci;

.fieati m; I c p My invention relates to. telephonei systems and has to: do more particularly-with automatic or semi-automatic systems in which switches are used for connecting a calling line to an idle trunk, and an objectof. my invention is the provision ofan improved a1,-

rangenient which embodiesndesirable Qfea tures andiadvantages, all in, anreflicient, simple and economical manner, and in which the switch of my invention is most positive in its operation. 4

Line switches oriindividiial' switches of it the present type are provided with off-nor: mal contact-s which are moved to their alternate positions during a period of fthe select-.

ing operation of the switch to bringabout the proper function of the saini y andfla feature of my invention is; the provision of -ma'y, 'b'e had.tothe accompanying application. I

the trunk last used when a call is initiated,-

provided the trunk in the meantime hasnot been seized by another switch and is in use,

at the time the call is made Another feature of my invention isythe -:prov1s1on of means in the switch of myv in;

vention whereby, when a line is seized as, a called'line, its associated switch is operated to step itswipersinto eii'gagementwith'the.

next idle set of contacts, should its wipers be the switch in establishing a connection for the line as a calling line, in the event that the said contacts were seized by another switch between the lapse of time that the line was a calling and a called line. In theeventuhat or partialactuation I p V i are-attained, will be described-by reference to the accompanying drawing, in which I engaging contacts of the trunk last used bythese idle "sets 'ofcontacts as now engaged by the switch wipers: be appropriated by another. switch'during the time that the line isconnected in circuit as afcalled line, the i said contacts willbei, bu sied and the switch. will operate immediately to ste thewipei's in search of the next set of idle contacts leading to an idle trunk so that when the calledline wishes: to recall immediately upon I disconnection the wipers .will be engaging an idle setof contacts leading to an idletrunk, thus materially reducing the time in extending the connection of the recalling line to an idle trunk.

:Another the switch. to stop on busy contacts nor to pass over idle'contacts. The above features of my-invention, as well as others, will be more fully hereinafter described. The non-restoring switch of my invention isiiof the generalfltype illustrated and described inapatent vto Harry H; Ide, issued Oct 21, 1924, No.-l,512,101, andfor a'more complete description of the switch reference feature of my invention is the" provision of a switch with a positive drive circuitthat does not permit the 'wipersof T he ,9 novel features of the invention, through the, provision of which the abovementioned; and otherfadvantageous results illustrate diagrammatically an automatic telephone system includingthe line switch of my invention. v 1 v Referring now more in detail to my inof the callingdevice CD. The calling subrotary shaft which carries the test or private i e 2 and a air of line wipers 3 andA.

A, line relay LR is providedwhich is encr- ,ioo fgized over the subscribers line conductors, and a.,cut-ofi relay CO '15 also provided which isienergizedwhen" an idle trunk is seized to extend the connection from the call-- 7 'ing substation to the seized trunk. A motor magnet MM is provided for stepping the,

wipers 2, 3 and i of the switch B step by step over the bank contacts 5, 6 and 7 of the switch.

The connector C comprises an impulse relay IR, which relay IR is energized over the line when an idle connector as C is seized and is de-energized and energized by impulses from the calling substation A to bring about the primary movement of the wipers 8, 9 and 10 through the agency of the primary magnet PM. A switching relay SlV is provided which, when energized, connects the secondary magnet SM to be acted upon by impulses to step the wipers 8,- 9 and 10 in a secondary direction over contacts 11., 12 and 13 to engage the contacts of the called line. A test relay TR is provided with tests the called line as to its idle or busy condition, and, when busy, connects a suitable busy tone from the busy-back apparatus BB to notify the calling subscriber as to the busy condition of the called line. A ringing control relay RC is provided, which connects the ringing generator RG and interrupter I in circuit to intermittently apply ringing. current to the called idle line. A supervisory relay SR is also provided which is energized when the subscriber at the called substation answers. Primary off-normal contacts PON are provided, which assume their alternate position upon the first step of the wipers 8, 9 and 10 in a primary direction, and secondary olf-normal contacts SON are also provided, which assume their alternat position upon the first step of the wipers 8, 9 and 10 in a secondary direction.

To the right of the drawing I illustrate a called substation D similar to the calling substation A, which connects at the exchange into a line circuit B similar to that of B.

Having described in general the apparatus as illustrated in the accompanying drawing, I will now describe in detail the operation of the system including the indi vidual switch of my invention.

Assuming now that the subscriber at the calling substation A initiates a call, the removal of the receiver thereat closes an energizing circuit for the line relay LR of individual line switch B, traced from battery through the winding of relay LR, conductor 14, normal contact 15 ot the line relay LR, conductor 16, normal contact 17 of cut-ofi relay CO, through the substation A, back through normal contact 18 of relay CO, conductor 19, normal contact 20 of relay LR, conductor 21 to ground at normal contact 22 of relay 23. lVipers 2, 3 and 4: rest upon the set of contacts 5, 6 and 7, last used by the line as a calling line or in engagement with a set of contacts which were engaged by the wipers when stepped into engagement therewith when the line of subscriber A was seized as a called line, as will be more fully hereinafter described. Assuming that the contacts 5, 6 and 7 upon which the wipers 2, 3 and 1 now rest are busy due to another subscribers line circuit having selected that connector, the engaged private contact 5 will be grounded. Energized line relay LR now closes its alternate contact 2%, establishing an energizing circuit for the relay 23, traced from battery through the winding of relay 23, conductor 25, normal contact 26 of relay CO, conductor 27, alternate contact 24: of relay LR, conductors 28 and 29, wiper 2 and to the grounded busy contact 5. The relay 23 upon energization closes its alternate contact 22, establishing an energizing circuit for the motor magnet MM, traced from battery, normal contact 30 of motor magnet MM, through the winding of motor magnet MM, conductor 31 to ground at alternate contact 22 of relay 23. The motor magnet MM upon energization steps the wipers 2, 3 and 4 into engagement with the next set of contacts 5, 6 and 7, and should the contacts now engaged by the wipers be busy the relay 23 will continue energized and the motor magnet hIM will set up a vibratory circuit for itself due to the opening and closing of its normal contact 30, and the magnet MM thus steps the wipers 2, 3 and 4 from one set of contacts 5, 6 and 7 to the next as long as busy, i. e., grounded contacts are encountered, since as long as grounded contacts 5 are encountered by the wiper 2, relay 23 will remain energized and thus keep the vibratory circuit of motor magnet MM closed. The line relay LR has its initial energizing circuit opened at its own contacts 15 and 20 and at normal contact 22 upon the energization of relay 23, but the line relay LR being slow to release is held up momentarily until a substitute circuit is established for it, traced from ground at alternate contact32 of relay 23, conductor 14- to battery and ground through the winding of relay LR. The ground at alternate contact 32 of relay 23 also extends over conductor 14, normal contact 33 of relay CO, conductor 35, and to the calling lines private normal contacts 36 at the connectors having access to it to render such contacts busy against select-ion.

\Vhen an idle private contact 5 is encountered by the wiper 2, the relay 23 will restore as the contact 5 now engaged will be free from ground, and the opening of its alternate contact 22 prevents further actuation of motor magnet DIM. The opening of alternate contact 32 opens the energizing circuit of line relay LR, but the relay being slow to release is held energized momentarily closing an energizing circuit for the cutoff relay CO, traced from battery through resistance 37 and winding of cut-off relay CO, alternate contact 20 of relay LR, conductor 21 to ground at normal contact 22 of relay 23. The line relay LR upon restoration opens the initial energizin stitute circuit is established for the said relay 0.0, as will presently be described. The relay-23 upon de-encrgization and relay CO upon its energization remove the busy ground from contacts 36, butthcclosing of alternate contact 39 of relay CO connects ground to the contacts 36, keeping them busy until the termination of' the conversation. I 2

6 The relay CO having been-energized, its contacts 17 and 18 assume their alternate positions and the wipers 2, 3 and 4 of the individual switch B now connect to the contacts 5, 6 and 7 of the idle connectcr thus extending the calling line to the seized idle connector C. A circuit is established for the impulsc relay IR of the connector C, traced from battery through the left-hand winding of relay IR, contact 6, wiper 3, alternate contact 17 of cut-oil? relay CO, through the substation A, back through al ternate contact 18 of relay CO, wiper 4, contact7, to ground through the right-hand winding of the impulse relay IR. The clos ing of alternate contact 40 of the impulse relay IR establishes energizing circuits forthe relays 41 and 42 of the connector 0, the circuit of ,relay 41 extending from battery through the right-hand winding of relay 41,

conductor 43, normal contact44 of primary. oil-normal contacts PON, conductors 45iand 46 to ground at alternate contact 40 of the: impulse relay IR. The circuit of relay 42' extends .jfrom battery through the lowerv winding of relay 42, jc'onductors .47 and; 4 8, alternate contact 49 of relay IR, to ground at alternate contact 40 of impulse relay 1R.

Therelay 41 upon 1 energization closes a locking circuit for itself, traced 'fromibattery through the right-hand winding of relay 41 to ground at alternate contact 50 of said relay 41. The closing of alternate conf tact 40 of impulse relay IR establishesa' substitute energizing circuit forcut-oiffrelay C0 of theindividual line switch: B, ibefore Lit has time to deenergize, which may be traced from battery through the resistance. 37, and winding of the cut-off relayCO, its alternate contact 38, conductor 29, 'wiper.;2-,

contact .5, conductors 45-and 46 to ground at alternate contact 40 of the impulserelay IR, the said relay CO remaining energized until the termination of the conversation.

If the private contact 5"e'ngaged by the wiper 2 is idle when the subscriber fat the substation A initiates a call, the li ne relay LR is energized, as before described, and op.- crates to closeits. alternate contact 24, but as there is no ground on the privatecon tact 5, no energizing: circuit'is established for the relay 23and therelay 23 remaining inert its alternate contact22 remains open,

preventing an energizing circuit being established for motor magnet MM, and the wipers 2, 3 and 4, therefore, remain in engagement withthe contacts 5, 6 and? that were last used? by the switch B in cstablishing a connection, or inconnection with a set of contacts 5, 6 and 7 to which the said wipers 2, 3 and 4 were advanced, in the event that the substation Awasa called line, as will be more fully hereinafter described. The cut-- off relay CO is, therefore, immediately, energizcd from battery through the cut-off relay G Oto ground at normal contact 22 of relay 23, as before'des cribcd, and the operation of the circuit from this point on is the same as above described, it being noted that contact 24 is arranged to close enough ahead of20 so that relay 23 will operate before relay CO, has a chance to operate, ifthe contact 5 is busy, J Thus the switch only travels when its wipers 2, 3 and 4 are in engagement with a busy trunk when a call is initiated. 7

Assuming now that the substation A is selected as a called line by a connector-which has engaged contacts 36, 12 and 13 and this ground extends from the connector which seized the contacts ofthe-substation A as a called line to the contact 36, conductorT35, normal contact33 of cut-off relay CO,-con-, ductor 14 and through the winding of line. relay LR to battery. The line relay LR upon energization closes its alternate contact 24, and should the private wiperc2 of the'line switch B be engaging a busy contact 5 at the time the substation is fseized' as a called line, an energizing circuit is ,estab-".

ing circuit for the motor magnet MM, traced from battery at normal contact 30 otmotor magnet MlVI, through the winding of magnet MM,- conductor 31 to ground at alternate contactx22aof relay-23. The motor magnet MM is thus energized and, through the me dium of the usual ratchet and pawl mechanism, steps the wipers 2,3 and 4 into engagement with the next set of contacts 5, 6 and 7 The magnet MM upon energizationopens its normal contact 30 and 'as long as the "private wip'cr 2 cngages successive busy contacts 5, the

relay 23 will remain energized and the motor I magnet MM will establish-a vibratory circuit for itself through its normal contact 30 to step-the wipers 2, 3 and 4 from one set of contacts 5," 6 and 7 to the next, 'untilthe anon-busy or non-grounded 1 lay 23 restores and the opening of alternate contact 22 of said relay 23 prevents further energization of the motor magnet MM.

hen the substation A is seized as a called line, the line relay LR of its associated individual line switch B is energized, as before described, and it the wipers 2, 3 and 4 of the switch B are resting on an idle set of contacts, no energizing circuit is established for the relay 23 of the switch B. The cut-oft relay CO does not energize at this time due to the short circuit around it, which extends from a direct ground at contact 36 of the connector, over conductor and through normal contacts 33 and 34 to one terminal of the winding of the relay CO, so that the circuit traced from ground at normal contact 22 of relay 23, conductor 21, alternate contact 20 and to the other terminal of the winding of cutoff relay CO to battery, does not avail to energize it.

Assuming that the substation A has been seized as a called line and the motor magnet MM has actuated to step the wipers into engagement with an idle set of contacts and that during the time that the substation A is in conversational circuit as a called line the set of contacts 5, 6 and 7 now engaged by the wipers 2, 3 and 4, as before described, are appropriated by another calling line switch, ground will be placed upon the private contact 5 of the contacts just seized, as previously described, and this ground will extend through wiper 2 over conductors 29 and 28, alternate contact 24 of line relay LR, conductor 27, normal contact 26 of relay CO, conductor 25 to battery through the winding of relay 23. The relay 23 upon energization closes its alternate contact 22, establishing an energizing circuit for the motor magnet MM, which now steps the wipers 2, 3 and 4 over successive sets of contacts 5, 6 and 7 until an idle set is seized, as previously described. It will thus be seen that when a substation line has been busy as a called line, it will at the end of conversation have its line switch resting in engagement with an idle trunk line, and the line switch of the calling line will, of course, also be upon an idle trunk. The cut-oi? relay CO also remains at normal during the stepping of the wipers 2, 3 and 4 over contacts 5, 6 and 7 when the substation A is seized as a called line as during the movement of the wipers 2, 3 and 4 in their act of rotation in seeking an idle set of contacts, the relay 23 is energized and the circuit of cut-off relay CO is opened at the normal contact 22 of the energized relay 23, and no actuation of relay CO takes places. The energization of relay IR having brought about the energization of relays 41 and 42, as already described, assuming that the called subscribers number at substation l) is 45, the subscriber A now operates his calling device CD to send tour impulses of current over the line. These four impulses bring about four de-energizations and energizations of the relay IR, causing the primary magnet PM to energize and de-energize four times to step the wipers 8, 9 and 10 in a primary direction to the fourth group of contacts, that group containing the contacts of the called line. The circuit of the primary magnet PM may be traced from battery through the winding of the said magnet PM, normal contact 51 of switching relay SIV, conductor 52, alternate contact 53 of relay 42, normal contact 49 of relay IR, conductor 46, conductor 45, and normal contact 44 of the primary off-normal contacts PON to ground at alternatecontact of relay 41.

Afterthe primary off-normal contact 44 has moved on the first step of the switch shaft, the ground fed from normal contact 54 of relay 55 is substituted for the ground fed through contact 50 of relay 41. After the last impulse of the series has been sent, the steady flow of current through both windings of relay 42 causes the said relay 42, due to its difierentia-l action, to neutralize and restore its contacts to normal. Relay 42 does not restore during the sending of impulses due to its adjustment, construction and the rapidity of the interruptions of contact 49. It will be noted that the relay when first energized had its upper winding immediately energized by contact 50 of relay'41 and was in a neutral condition with its armature retracted when relay IR sent the first impulses, but immediately energized when relay LR opened the circuit of relay 42s lower winding. The closing of normal contact 56 of relay 42 brings about the energization of the switching relay SW by current traced from battery through the winding of said relay SIV, its makebeforebreak contact 57 normal contact 58 of secondary oiT-normal springs SON, conductor 59, normal contact 56 of relay 42, and conductor 60 to ground at alternate contact 61 of primary ofi-normal contacts PON, the said primary off-normal contacts PON having been moved to their alternate position on the first step of thewipers 8, 9 and 10 of the connector switch olt normal. The closing of alternate contact 51 of the switching relay SIV now renders the secondary magnet SM operative so that when the calling subscriber at the substation A actuates his calling device again to send the last set of impulses, which we have assumed are five in number, the said magnet SM will be energized and de-energized by the impulse relay IR five times over a circuit traced from battery through the winding of the said magnet SM, alternate contact 51 of relay SW conductor 52, alternate contact 53 of relay 42, normal contact 49 of relay IR, conductor 46, conductor 45, and; hrerfiatf'qcbttact of the priniary oil-normal contacts PON and conductor 62 to ground at "normal contact togfrelayfifi, The secondary magnet- SM now stepsthefwipers' 8; 9 and 4 "the alternate contact 64 of relay SW, alter- ,fss

' Irate contact5 8 Rofthe secondary othnorinal contacts SOY (said, contacts haying been moved to their alternatejposition 'upo-nthe first step of the ipers in their Secondary direction) conductor 59, normal, contact 56 of relay 42, conductor 60 to grounld at alternate contact 61 of the primary off-normal contacts PON. The closing .of alternate contact 65 of relay TR connects the'said relay over conductor 66 to th'e'test, iper 8,

and should the called linebe busy the pri- 1 yate contact 11 of the called line Wouldbe grounded, thus closing a locking circuit for relaylTRthroug'h the private Wiper.

' GaZ Z ed Zine: 7

Assuming that the called ts is idle, priyate contact, 11 of the; called line willhave a lbatteryipotential uponit, andthe relay will not remain energized but will [deenerg1ze.f The open ng of normal 'contact G7 fof relay TR opens the circuit of the switchingrelay SW. The relay SW deenergizes and opens the circuit for relay TR at its contactfi, leaving therelay TR dependent upon the potential found upon. the

fprivate contact 1 1 of the called line for its holding potential, and, as assumed, this con;

tact is treefrom ground potentialr tl ere fore, the relay TR de-energizesand returns to normal. The relay {TR deenergizi ng causes the energization of the relay 55' over a circuit which may be traced from bat.- tery throughlthe Windingof line relay LR, conductor 14', normal contact 33', conductor 35, banl; contact'll, Wiper 8', conductor 66', normal contact65-of relayT R, conductor 70, normal contact 71 of relay SW, conductor 72, throughthe lower -Winding of the relay 55, and conductor 73 .to ground at alternate contact 74 of relay 41. The clo's ing of alternate contact 75-015 relay 55 shortcircuits the lower Winding of the said relay, and the'c'l'osing of alternate contact '7 6 of relay 55 closes a circuit thrOughthe. upper Winding; o f- 'the said relayfthroiigh the almitatecontact '76; and conductor???) to ground alternate contact 14 relay The" line relay LRibf the""lirfe swit ch B i sociat edjwith the called line'is energized oyer this jcircuit and remains energizedulr til conversation has terminated.

The closingjof i alternate contact 77 of relay"55 connects thei'nterrupter I to vthe relay 78 andthe circuit for relayf78 may be-traced from battery through the Winding of the said relay 78, conductorTS), alternate contact 77' of relay 55, conductor 80, normal contact 81 of relay-RC and through the interrupter I to ground. The relay 78 is thus intermittently energized and de-energized by the rotating interrupter I, and upon each of, relay T8, wiper 10, bank contact 13,

through the condenser and call bell of the called sub station D back through bankl Qcontact 12, iper 9, normal contact '87 of relay 78, and, conductor 88 to ground at alternate contact 54 ofrelayfl5 5.

The call bell of [he called subscriberrat the substation D is thus intermittentlyrung, due to the energization and de-energization of the relay'78 by'theinterrupterlI. WVhen the called subscriberj answers I, and the relay 78 is in its energized position, a circuit for the relay SR is closed,fi which;maybe traced Ifronli battery throught theflower winding of the relay through alternate contact deenergization of the relay. 78 the rhiging generator 15 connected to the called l ne 86of, relay '1 8, Wiper 10, contact 13, through the now closed contacts of the substation sivitchhook at the called' substationD, back through contact 12,wiper.9, alternate contactj8fof relay ,7 8, and through the upper winding ofQthe, relay SR to groundg The 'rela U SE n on ener izin closes an enerv y .7 r t by, r

B JI' w ich ma be tr r m ba t y th ghflthe wind ngo the s re y its. make-beforebreak contact. 89 to ground at alternate contact QO ofJrelay SR. The

closing ofialternate contact 91L ofrelay closes 1 a locking] circuit for the said relay RC1 which, maybe traced" from battery through the Winding of the said relay, its alternate contactfil and conductor 60 to groundat a1ternatecontact61 ofthe pri} mary off-normal contacts PON. The open? contacts PON. The subscribers are now in conversational circuit, and the talking circuit may be traced over the heavily marked conductors, said conductors having the condensers K and K interposed.

The subscribers having finished conversation, and assuming that the subscriber at the calling substation A is first to replace his receiver upon the switchhook, the opening of the switchhook contacts brings about the de-energization of the impulse relay IR of the connector C. The restoration of the relay IR brings about the opening of the holding circuit of the relay C0 of the individual switch B, which relay CO restores and places the individual switch B in condition to be used in establishing another connection.

The subscriber D restoring his receiver upon its switchhook interrupts the circuit of the relay SR at the switchhook contacts, causing the said relay to de-energize. The closing of normal contact 95 of relay SR closes a circuit through the lefthand winding of the relay 41, which may be traced from battery through the left-hand winding of the said relay 41, alternate contact 96 of relay 41, conductor 97, normal contact 95 of relay SR and conductor 98 to ground at normal contact 40 of relay IR. Due to the differential construction of relay 41, the said relay neutralizes and restores to normal. The closing of normal contact 99 of relay 41 closes an energizing circuit for the secondary magnet SM, which may be traced from battery through the winding of said secondary magnet- SM, conductor 100, normal contact 99 of relay 41, alternate contact 101 of the primary off-normal contacts PON, through the interrupter I to ground. The secondary magnet SM thus steps the wipers 8,9 and 10 beyond the last set of contacts in the group and the wipers then restore to 0 normal from this position by spring tension. Therestoration of the relay 41 brings about the opening of the circuit of the relay 55 at alternate contact 74, and the relay 55 restoring opens the circuit of relay 78'at contact 77 of relay 55, and the primary off-normal contacts having restored upon the restoration of the switch, the opening of the alternate contact 61 of PON brings about the de -energization of the relay R0. The relay 41 also brings about the deenergization of the line relay IR of the line switch B which is associated with the called subscriber D. All the apparatus used in establishing a connection between a calling subscriber at the substation A and the called subscriber at the substation D is now at normal and available for use in establishing other connections.

Assuming now that the subscriber at the called substation was first to replace his receiver upon the switchhook, the opening contacts. The relay IR de-energizing closes a circuit for the left-hand winding of relay 41, causing the said relay to de-energize, as hereinbefore described. The restoration of the individual switch B and connector 0 is the same as previously described from this point 'on. Should the called subscriber D fail to replace his receiver upon the switchhook after the conversation is terminated,

the replacing of the receiver at the substation A brings about the de-ener'gization of the impulse relay IR of connector C, the same as before, and the opening of alternate contact 40 of impulse relay IR opens the circuit of the relay CO of individual switch B, as before described, and causes the release of switch B.

The subscriber at the called substation failing to replace his receiver, permits the continued energization of the relay SR, thus holding the contact 95 ofsaid relay in its alternate position, preventing the difl'erent-ial wound relay 41 from restoring to normal and closing the energizing circuit for the secondary magnet SM. The relay 42 energizes when the line relay IR drops back but is immediately restored to normal due to the closure of an energizing circuit through the lower winding of the said relay 42, which may be traced from battery through the said lower winding, conductor 47, alternate contact 95, connector 98, to ground at normal contact 40 of the now restored impulse relay IR. Relay 42 being difierentially wound, restores to normal, and the closing of normal contact 102 of the said relay 42 places a ground upon the private contact of the connector C over a cir cuit which may be traced from ground at alternate contact 61 of the primray oil-normal contact PON, conductor 60, normal contact 56 of relay 42, conductor 59, alternate contact 58, normal contact 102 of relay 42, alternate contact 103 of the secondary oil'- normal contacts SON, to the private contact 5. The placing of this busy potential upon the private contact prevents any individual switch B from engaging the contacts of this busy connector.

Called Zine busy.

Assuming now that the called line is busy, the operation of the circuit is the same up to and including the time that the relay TR momentarily energizes. The line being busy, the private contact 11 has a busy ground potential placed upon it, thus clos- Til ing alocking circuit for the testrelay TR from battery through the winding of the said relay, its alternate contact 65, conduce tor 66, and the wipers to ground at contact 11. The closing of alternatecontact 1040f the test relay TR connects the busy-signal BB to the line to transmit a busy signal to said calling subscriber at substation A, thus notifyinghim'of the busy condition of the said called substation D. The relay Tit upon'locking to ground at the private contactll, closes a circuitfit'or relay R0, traced from battery through the Winding of relay RC, make-befOre break contact 89,'normal thus closesa locking circuit for itse lf, traced up to ground at contact 61.

contact 90 of relay SR, normal contact 64 of relay SW, conductor63, alternate contact 65' of relay TR, and conductor 66. to the grounded private contactl l. The relayEU I opens the circuit of the relayCO ofthe individual switch B to place the switch in condition for establishingother connections as previously described. The relay IR de energizing brings about the restoration of the relay 41, due to the fact that the relay SR has not been energized. The closing of the circuit through the left-hand winding of the circuit 41 brings about the neutralization of said relay &1. The closing of normal contact 99 of the said relay 41 closes a circuit through the secondary. magnet SM, which magnet steps the wipers 8, 9 and 10 beyond the last set of contacts. The wipers then restore to normal by spring tension. The primary off-normal contacts PON and secondary off-normal contacts SON are also restored, and the apparatus used. in this busy connection is now at normal and avail-1 able for use in establishing other connections. n

The individual line switch circuit B associated with the called line 'D is similar in operation to that of line switch B asso ciated with the calling line A, vthe material difference being in What is sometimes called a positive drive circuit. This positive drive circuit is under the control of the motor magnet MM and the relay 23C, The

line relay LR energizes either when the substation I) is a calling or a called line. First assuming that line is a called line, the

vidual line switch '13 relay'LR is energized as.before described and, assuming that the private wiper 2 is engaging a busy contact 5, ground from the grounded contact 5 will extend through wiper over conductor 29', alternate contact'2atof relay LR, conductor 27', normal contact 26 of cut-off relay C0, conductor 1 25, "norma-l contact 110 of motor magnet MM, conductor 111 and through the wind ing of relay 23 to battery. The relay 23 upon energization closes its alternate con tact 32, closing an'energizing circuit for the motor magnet MM, which steps the wiper into engagement with the next set of contacts. The magnet MM upon energization opens the. energizing circuit of relay 23 at its normal contact 110 and allows relay 23 to restore, and relay 23 upon restoration opens the energizing circuit of relay MMat its alternate contact '32. Now, should the wipere' engage another busy contact 5, relay 23 'willvagain energize, which in turn will energize magnet MMandthis see-saw "action of relay 23 and magnet MM will.

continue until a private contact 5 is seized;

From the foregoing it will be seen that re lay23-"bnlyoperates when a busy private contact .5 is engaged, and magnet-MM lS only energized wheirrelay 23 1s energized,

andwhen an idle contact is engaged *relay L 23 remains at normal, andthus' niagnetiMM will faillto energize, and the wipers will not stop 'ona busy contac-torpzts's an idle one; The' circuit operation of the indias to theyoperation of the cut-off? relay CO and its circuit functions, are the same in general as those of line switch B andit is thought, willxbe sufficiently apparent without further de I tailed description. 1

While I have referred to relayCO as a cut-off relay having generally in mind its function of cutting the line 01f from the line relay, it will be observed it might'well be called a line cut on relay because it connects the lineon to the wipers. accordingly in the claims refer to it in the I shall latter way when I wish particularly to note 7 its latter function.

I do not intend to limit nayself to the particular embodiment of my invention herein shown and described, as it maybe readily employed in various modifications.

What I claim as new and desire to secure byiLetters Patent, is:

1., In a line circuit for telephone systems, a relay for energization to extend the line limbsywhen the line is a'calling line, multi ple terminals for said line as a called line and a. link circuit terminal adapted to be applied to one of said multiple terminals, means associated with said link circuit to short-circuit said relay when so applied, and amotor magnet, saidrelay energizable to prevent the operation of said motor magnet and de-energizable to permit said motor magnet to operate and to also permit a calling line to be connected to said line circuit at the same time, said motor magnet being operable even though a calling line is connected to said line circuit.

2. In a telephone system, a line switch and associated circuit controlling relay, a connector operable responsive to directive impulses to select said line, said connector having means to short-circuit said relay when the line is idle, a second relay for said switch controlled by said controlling relay, and a motor magnet controlled by said second relay, said second relay and said motor magnet adapted to operate alternately to progressively advance said switch.

3. In a telephone system, a subscribers line circuit and controlling relay therefor, and an associated automatic selecting switch operated by current over said line, controlling means short-circuiting said relay while said switch travels, and other means controlled over another subscribers line circuit for short-circuit-ing said relay.

4. In an automatic telephone system, a telephone line and an automatic switch adapted to travel in response to said lines control, a relay short-circuited while said switch travels, and a selective switch operable by directive impulses over another line having means to short-circuit said relay.

5. A telephone system including a relay adapted for energization over a link circuit, talking circuit contacts controlled by said relay, means for short-circuiting said relay when said talking circuit is busy as a call ing circuit, and means for short-circuiting said relay when said talking circuit is busy as a called circuit.

6. In a telephone system, a line relay operated by current oveixthe line when the subscriber initiates a call or answers a call, another relay and means for short-circuiting said relay when the line is connected to as a called line, and a circuitfor said second relay controlled by said first relay.

7. An automatic telephone system including a telephone line and an automatic nonrestoring switch, a relay for said switch for extending the line limbs of said telephone line when the switch is operated to extend said line as a calling line, a connector switch for connecting to said line as a called line and provided with means to establish a shunt circuit about said relay when the line is connected to as a called line to prevent the extension of said line limbs, but to allow progressive operation of said switch.

8. A telephone system including a telephone line, an automatic non-restoring switch for said line, a motor magnet for operating said switch to extend the line towards a called line, a controlling relay for extending the line limbs of said line through said switch, a connector switch adapted to be connected to said telephone line as a called line and provided with means for establishing a shunt circuit about said relay when said telephone line is connected to as a called line to render said relay inoperable to prevent the extension of said line limbs but to allow progressive movement of said switch without interfering with the connection between the said connector switch and said line.

Signed by me at Chicago, in the county of Cook and State of Illinois, this 12th day of January, 1921.

LEROY D. KELLOGG. 

